In order to achieve high-speed packet transmission, a gigabit rate transmit/receive chip set (transceiver) must be employed. One such transceiver is a device sold by the Hewlett Packard Company headquartered in Palo Alto, Calif., USA, which makes and sells a transmitter designated as the HDMP-1022 transmitter and a receiver designated as the HDMP-1024 receiver. The HDMP-1022 transmitter and HDMP-1024 receiver chip set is described in detail in a 40-page Preliminary Technical Data sheet dated August 1996, distributed by Hewlett Packard and, at present, has been available on its Internet website. This data sheet shows how the HDMP-1022 transmitter and the HDMP-1024 receiver can be utilized as a gigabit, or G-LINK™ controller, to provide transmit and receive G-LINK serial interface operations. The G-LINK of the present invention is an upgraded G-LINK II.
An application of a G-LINK controller is shown in FIG. 1, which can be used in a set-top box. In the figure, a G-LINK circuit 10 serves as a serial interface circuit for coupling a conventional universal asynchronous receiver-transmitter (UART) circuit 12 to a G-LINK serial port 14 for a plurality of purposes, such as providing the UART 12 with a signal path and controls for converting from full duplex to half duplex communication to and from the G-LINK serial port 14. In addition, the G-LINK circuit 10 may relay infrared (IR) signals received from IR blaster source 20 via data line 21 for the G-LINK serial port 14 to drive an IR blaster (not shown).
All the components in FIG. 1 are controllable by an operating system (not shown) and the UART 12 is defined as a COM port. As such, when the UART 12 receives a signal, it generates an interrupt signal to be processed by the operating system. In one mode of operation such as in a configuration test mode wherein the configuration of the system is tested, the G-LINK circuit 10 forwards a test signal from the G-LINK serial port 14 to the UART 12. Under this mode of operation, the UART 12 should receive the test signal and generate interrupts accordingly. However, in another mode of operation, such as in a demonstration mode wherein a user is educated on the use and capabilities of the system, the G-LINK circuit 10 unnecessarily transmits signals it receives from the UART 12 back to the UART 12. This unnecessary feedback causes the UART 12 to generate unnecessary interrupts to be served by the operating system. The processing of these unnecessary interrupts may degrade the performance of the set-top box. Thus, there is a need to control the communication between the G-LINK circuit and the UART 12.